import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 666
 * Date: 2023-04-08
 * Time: 21:25
 */
public class test3 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n  = scanner.nextInt();
        System.out.println(fiBo(n));
    }
    private static int fiBo(int n){
        if(n==1 || n==2){
            return 1;
        }
       return fiBo(n-1)+fiBo(n-2);
    }

}
